If you want to use this package as your default system ruby, as root
create symbolic links like so (overwriting any previous default):
 ln -sf ${PREFIX}/bin/ruby20 ${PREFIX}/bin/ruby
 ln -sf ${PREFIX}/bin/erb20 ${PREFIX}/bin/erb
 ln -sf ${PREFIX}/bin/irb20 ${PREFIX}/bin/irb
 ln -sf ${PREFIX}/bin/rdoc20 ${PREFIX}/bin/rdoc
 ln -sf ${PREFIX}/bin/ri20 ${PREFIX}/bin/ri
 ln -sf ${PREFIX}/bin/rake20 ${PREFIX}/bin/rake
 ln -sf ${PREFIX}/bin/gem20 ${PREFIX}/bin/gem
 ln -sf ${PREFIX}/bin/testrb20 ${PREFIX}/bin/testrb
